Thomas Henry Huxley, (born May 4, 1825, Ealing, Middlesex, England—died June 29, 1895, Eastbourne, Sussex), English biologist, educator, and advocate of agnosticism (he coined the word). Huxley’s vigorous public support of Charles Darwin’s evolutionary naturalism earned him the nickname “Darwin’s bulldog,” while his organizational efforts, public lectures, and writing helped elevate the place of science in modern society.

Thomas Henry Huxley, born above a butcher’s shop, was the youngest of the six surviving children of schoolmaster George Huxley and his wife, Rachel. Although Huxley received only two years (1833–35) of formal education at his father’s declining Ealing School, its evangelicalism later marked his scientific rhetoric. From 1835 his father tried managing a bank in his native Coventry, which left Huxley footloose in the ribbon-weaving city. Huxley’s parents were Anglicans (members of the Church of England), but the boy sympathized with the town’s Nonconformist (or Dissenting) weavers, who wanted religious equality and an end to the Anglicans’ control of public institutions. Fascinated by science and religion, he studied Unitarian works, whose cause-and-effect explanations and denial of the duality of spirit and matter challenged the socially conservative views dominant in natural history and natural theology. Thomas Carlyle’s books taught Huxley that the religious feeling of awe was distinct from theology, which dealt with gods and miraculous events. The teenager speculated (as did radical Dissenters) that morality was a cultural product, which left it open to a scientific explanation. These were the seeds of Huxley’s agnosticism, scientific enthusiasm, and understanding of sectarian power play.

The longhaired student was apprenticed (c. 1838–41) to his sister Ellen’s beer-swilling husband, John Charles Cooke, a medical materialist. Transferred to a London dockside practitioner early in 1841, Huxley was shaken by the lives of his pauper patients. Even at the back-street anatomy school where Huxley took the botany prize in 1842—Sydenham College, off Gower Street in London—there was no escaping sectarian politics and science; Sydenham’s owner, Marshall Hall, was studying mechanistic reflex arcs while haranguing the Royal College of Physicians for excluding Dissenters from its fellowship.

On a free scholarship (1842–45) to Charing Cross Hospital, London, Huxley won medals in physiology and organic chemistry. His own mechanistic bent showed as he sought to explain living processes by physicochemical laws, and his superb microscopy was revealed in his discovery in 1845 of a new membrane, now known as Huxley’s layer, in the human hair sheath.

The Rattlesnake voyage

To repay his debts, he entered the navy and served (1846–50) as assistant surgeon on HMS Rattlesnake surveying Australia’s Great Barrier Reef and New Guinea. With his microscope lashed to a table in the chart room, he studied the structure and growth of sea anemones, hydras, jellyfish, and sea nettles such as the Portuguese man-of-war, which decomposed too quickly to be studied anywhere except on the high seas. He grouped them together as Nematophora (named for their stinging cells), although they were later classified as the phylum Cnidaria (or Coelenterata). Demonstrating that they were all composed of two “foundation membranes” (shortly to be called endoderm and ectoderm), he even suggested that these membranes were related to the two original cell layers in the vertebrate embryo. The aristocratic Captain Owen Stanley, commander of the Rattlesnake, posted Huxley’s papers to his father, the bishop of Norwich, for London publication; but such old-style patronage galled Huxley, who insisted that science no longer needed aristocratic sanction.

A whirlwind romance in Sydney in 1847 left the sailor engaged to a brewer’s daughter, Henrietta (“Nettie”) Anne Heathorn. By now Huxley considered it a moral duty to weigh the evidence before believing church dogmas, and his skepticism worried Nettie. He sailed to the Great Barrier Reef and southern coast of New Guinea, sketched Papuans, and suffered terrible mental collapses in the broiling heat of the Coral Sea as he worried about the worth of his scientific work. But he continued his pathbreaking observations, noting that the larval sea squirt has tail muscles like a tadpole’s. This, in later years, would be part of the proof that sea squirts, or ascidians, are the ancestors of the vertebrates.

Huxley returned home in 1850, hoping to earn enough to bring Nettie to England. His success at the Royal Society of London testified to the meteoric rise of his scientific reputation: elected a fellow in 1851, he was its Royal Medal winner in 1852 and a councillor in 1853. But it was all praise and no pudding, he fumed. Although the British Treasury put him on half pay to finish his research (which appeared in 1859 as The Oceanic Hydrozoa), Huxley could not find an academic post in science. Such jobs were rare when Britain’s Oxbridge-trained leaders studied classics and when the public (privately funded) schools considered science dehumanizing. This led Huxley to more crushing depressions and a desire to raise science to a paying profession. Huxley took sides on the controversial issues of the day. He insisted that sea nettles were individual organisms, not colonies. He denied that the skull was composed of vertebrae, as his rival, the comparative anatomist Richard Owen, believed. Following the geologist Sir Charles Lyell, Huxley challenged the view that fossils showed a progression through the rocks, and he went on to repudiate a Christian-based geology that made humans the culmination of Creation. Marian Evans (the novelist George Eliot), writing alongside Huxley on the rationalist Westminster Review, an influential magazine at the cutting edge of 19th-century literary Britain, saw his brilliance as counterpoised by a love of provocation.

After four increasingly difficult years, Huxley’s professional fortunes improved in 1854. He began teaching natural history and paleontology at the Government School of Mines in Piccadilly, central London. With a new professional ethos sweeping the country, Huxley trained schoolmasters in science and fostered a meritocratic, exam-based approach to education and professional advancement. He simultaneously occupied chairs at the Royal Institution and the Royal College of Surgeons, and he organized public lectures for workers, themselves looking for a new, liberating science. His situation stabilized, he brought Nettie to England, and their eight-year engagement ended with their marriage in 1855.

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